A Color Reflectance Model And Its Use For Segmentation

Abstract

This paper presents a color reflectance model and demonstrates its usefulness for segn~entation. I adopt general physical models which describe the interaction of light with matter. These models apply to both metal and dielectric materials. The models indicate that, in general, reflectance is a complicated function of waveleiigth and geometry. An analysis of the general reflectance models, however, shows that approximate reAectance models exist which preserve much of the structure of the more detailed models. The approximate color reflectance model is the basis of an algorithm which is used during segmentation. This algorithm uses normalized color to classify surfaces according to milr terial composition. Experimen ta1,results are presented. electrics, ACRM is equivalent to the dichromatic reflection model suggested by Shafer [14]. In this paper, I use the Reichman body scattering model [13] to show that the dichromatic reflection model is a reasonable approximation for a large class of inhomogeneous dielectrics. I also show from the Torrance-Sparrow [17] specular reflection model and the Fresnel equations [2] that a unichromatic reflection model is a reasonable approximation for metals. Thus, ACRM combines the dichromatic reflection model for inhomogeneous dielectrics with a unichromatic reflection model for metals. The analysis includes an estimate of the accuracy of ACRM for various materials. An algorithm is derived from ACRM which is used to classify image regions based on the material of the corresponding object surfaces.